[slashmaster]

I ultimately want a machine that fully automatically changes tools with mach3. I know it has been done with the X2 with an r8 spindle. Is r8 the best for this? Someone told me that you can't do this with x3, rf-45 and bridgeport size heads because if you mounted a air cylinder to push the drawbar down it would push the whole quill down instead. I don't totally understand why. They said the very best you can do for X3, rf-45 and bridgeport size machines is a manually controlled impact wrench mounted to the top. Is this all true?

[thackman]

The R-8 and MT tapers that are commonly found on small mills have a number of limitations and were not designed for automatic tool changes. If you are looking for something that was designed for tool changes you will have to look for commercial machines like a Haas w/ CAT 40, 50 etc spindles but offhand I don't know of any hobby mills ($10k and under) with anything other than R-8 or MT. R-8 can be adapted to automatic tool change but as you have heard it usually requires and impact wrench or similar to tighten and loosen the drawbar. I think Syil was working on something for their mills (R-8) but I don't know if it was ever released.

First issue is with repeatable tool length. Since the collet is riding on a taper each time you swap tools, even the same tool, you may end up with a different zero point. Lucky this can be easily solved with the Tormach Tooling System (TTS) or similar adapters. It uses a special 3/4" collet and a set of adapters w/ flanges the bottom out on the face of the spindle.

The next issue is how to turn the drawbar. If you use a single collet and a set of straight shank adapters like the TTS system it's possible to use an air or hydraulic system and bellville washers to tension the drawbar/collet assembly but the challenge is doing it in such a way that the forces are all contained within the spindle shaft. If you start pushing up or down on the drawbar from the top all of the forces are transmitted directly to the spindle bearings and will cause premature failure. Picture taking the entire spindle out of the machine. A drawbar and collet would still be able to hold a tool because it's all self contained. If could put a cylinder on top but then it would have to be fastened to both the spindle and drawbar. That then means the entire assembly would need to be fully balanced and able to spin at full spindle speed. Then you have to deal w/ your hoses and fittings.
Then (if you have a square column mill) the Z-Axis has another 10-30 lbs that it has to lift and even if you have enough force in your steppers the additional mass will have impacted the Z acceleration.

Finally you need a tool changer mechanism to bring the tools to the spindle.

Tool changers on small and mini mills are possible, you just have to accept some of the tradeoffs. I have seen one or two tool changer kits for mini mills but they usually several thousand dollars. The impact wrenches don't have to be manual. You can get electronic valves that can be driven from a breakout board. There are two very good threads in the Tormach forum regarding tool changers and I think I've come across a few in other forums here on the zone.

Since an X2 is not very rigid to begin with and has a low top speed on it's spindle it's probably a fairly forgiving machine to build and ATC when you are running 0.25" endmills. An RF-45 you can take much heavier and deeper cuts which in turn will transmit far more force to the cutting tool. It's going to be much harder to design an ATC with enough clamping force to keep your 1" endmill or 2" facemill from slipping in the collet.

[groov]

Have you taken a look at the following site:

http://www.hossmachine.info/

Hoss the master of mods for X2 machines has designed and built an ATC ..I wish I have one tenth the mastery he has to do the same mods on my SX3.

groov

[philbur]

I think this may be true for any machine where you have used the quill to achieve the z-axis motion (depending of stepper torque and drive ratio vs air cylinder force). If z motion is achieved by moving the whole head then unwanted movement of the quill during tool changes will depend on how hard you lock/clamp the quill.

Phil

edit: if you are going to keep the machine manual as opposed to CNC then you would have to have a substantial lock on the quill, and use it every time you do a tool change. If you remove the quill return spring the quill will actually fall under it's own weight.

Someone told me that you can't do this with x3, rf-45 and bridgeport size heads because if you mounted a air cylinder to push the drawbar down it would push the whole quill down instead. I don't totally understand why.

[philbur]

The absolute best would be ISO30 etc. But R8 combined with the Tormach style holders works well enough for a couple of horse power I think.

Phil

I ultimately want a machine that fully automatically changes tools with mach3. I know it has been done with the X2 with an r8 spindle. Is r8 the best for this?

[Starleper1]

I'd be interested in knowing the tool change setup on a industrial VMC like a Haas or an equivalent. Im not talking about the rotary wheel where the tools are kept, either. I'm talking about that actual spindle setup.

[The Blight]

http://www.cnczone.com/forums/showthread.php?t=41200

[Starleper1]

A spindle like that would be a little more hairy to use with a ATC. Only because the spindle would have to have some sort of position sensor so that the keys line up every time.

[The Blight]

Not a problem with a servo as the spindle motor. These type of toolholders are what industrial machines use.

[escott76]

I'd be interested in knowing the tool change setup on a industrial VMC like a Haas or an equivalent. Im not talking about the rotary wheel where the tools are kept, either. I'm talking about that actual spindle setup.

The smaller HAAS's use the 40 taper mentioned earlier. Belleville washers to tension the grips, which are released by an air cylinder.
They DO have a position sensor, at least the ones I've worked with do. They have to in order to do things like rigid tap.

[pete from TN]

I am very interested in making a simpler atc for the Lathemaster mill once it is cnc. I also was planning on using the Tormach tooling to do so. I have removed the quill parts and do not intend to put them back once the machine is working. I am wondering about your statement that it cannot be done on the RF style machines. What, other than the quill drive is different about the X2 like hoss has as opposed to my Lathemaster mill. I was thinking I would devise a way to lock the quill into the millhead and use an air cylinder to unload the spring loaded drawbar very similar to the way hoss and others have done. Am I missing something here? Is there something about my spindle that is different than the X2 that makes this impossible? I am aware of the idea that the Tormach tooling may not be easily held in the machine since the cutting forces available on my RF clone are considerably higher than on the X2 X3 models but I have been using collets strictly for years and have not had an endmill pull out of the collet unless I did something wrong!! I was hoping to use the tormach setup and preload the drawbar to allow for a smooth release.

I was also thinking about another design of the air cylinder, possibly making my own design that would be considerably more compact and powerful enough to unload the drawbar. I would like to hear any ideas about this from you guys. The RF style machines are IMHO ideal machines for conversion and are large enough to take some decent cuts so I really was hoping to be able to go a long way with it.

I am also thinking about doing a custom belt drive conversion on this machine and I have been taking some measurements of the millhead and started drawing the idea on my cad, altho it still has a long way to go I am hopeful for an external belt drive with two speeds and a vfd much like the tormach uses. Anyone here done anything like this other than Cruiser? Thanks and peace...

[Teyber12]

an australian company was working on a x3 atc, anybody know what im talking about or what happened to it?

[SCzEngrgGroup]

I am very interested in making a simpler atc for the Lathemaster mill once it is cnc. I also was planning on using the Tormach tooling to do so. I have removed the quill parts and do not intend to put them back once the machine is working. I am wondering about your statement that it cannot be done on the RF style machines. What, other than the quill drive is different about the X2 like hoss has as opposed to my Lathemaster mill. I was thinking I would devise a way to lock the quill into the millhead and use an air cylinder to unload the spring loaded drawbar very similar to the way hoss and others have done. Am I missing something here? Is there something about my spindle that is different than the X2 that makes this impossible? I am aware of the idea that the Tormach tooling may not be easily held in the machine since the cutting forces available on my RF clone are considerably higher than on the X2 X3 models but I have been using collets strictly for years and have not had an endmill pull out of the collet unless I did something wrong!! I was hoping to use the tormach setup and preload the drawbar to allow for a smooth release.

I was also thinking about another design of the air cylinder, possibly making my own design that would be considerably more compact and powerful enough to unload the drawbar. I would like to hear any ideas about this from you guys. The RF style machines are IMHO ideal machines for conversion and are large enough to take some decent cuts so I really was hoping to be able to go a long way with it.

I am also thinking about doing a custom belt drive conversion on this machine and I have been taking some measurements of the millhead and started drawing the idea on my cad, altho it still has a long way to go I am hopeful for an external belt drive with two speeds and a vfd much like the tormach uses. Anyone here done anything like this other than Cruiser? Thanks and peace...

I see no reason you can't do a QC using belleville washers no matter what kind of machine you have. I suppose the issue being referred to is you have to press down on the drawbar to compress the bellevilles, to release the tool. If you have a quill, that force will tend to try to push the quill down. I'm really not sure how much of an issue this truly is, as you'd have to overcome the holding torque of your quill drive, and I doubt the force required is any greater than the machining forces anyway. But, there are several simple solutions to this in any case. First, you can have a solenoid-or air-operated quill lock that is actuated before the air cylinder that compresses the bellevilles. Or, use a second air cylinder to close a pair of jaws on the exposed end of the drawbar, to take the downward force, rather than allowing the spindle to take it. This would transmit the downward force directly to the head casting, rather than the spindle bearings. Both are quite simple and inexpensive to implement.

Regards,
Ray L.

[pete from TN]

I was really gonna find a way to fix the spindle in the millhead as if it came without a quill. The quill lock is stout but I am not sure it will have enough force to overcome the repetitive forces applied by the power drawbar. I was thinking I might pin the spindle somehow in the millhead as there are a myriad of points that have the necessary beef to make that strong. The quill has the splined shaft up top and I thought about a pulley arrangement that would be machined for a tight fit on thee splines and then a couple setscrews to secure it for the belt drive. The qc will be either setup with a bimba cylinder like hoss has or a custom arrangement that uses an o-ringed piston in a machined cylinder that is pressed into an aluminum mounting block that uses some of the multiple cover screws on top of the millhead to secure it. If the spindle is anything like the shapers I have r and r'd at work it is just a greased cylinder with pressed in bearings so no problem with loss of lubricant if you have to drill into the spindle body. It would also be nice to have a spindle lock for servicing the power drawbar. Something simple like a spring loaded pin that will engage into another hole in the spindle body thru the casting in front. These are just some preliminary ideas I have that I have not looked into fully but I think they might do the trick. The tormach tooling looks to be very nice and should work for my machine if it works for the tormach which is a similar design and I would think has similar power and torque specs. What say ye? peace

[pete from TN]

I had a paint malfunction in the process of refinishing my Lathemaster mill. I had to restrip the whole machine tonight and while I was working on the millhead I was thinking about the belt drive setup and the quick change setup. I have never removed the spindle on the machine and I already removed the quill drive mechanism. I decided it would be easier this time to remove the whole quill and tape the holes up for the repaint tomorrow. While I was working on it I realized that the spindle without the quill drive will literally fall out of the millhead so I took it out and had a chance to inspect it. This spindle is equipped with tapered roller bearings!! I thought it had the cheap ball bearings in it. This means that I can run this thing up to a reasonably high rpm with a belt drive and vfd. This also means that I can probably purchase some nice Timken or similar bearings for it and improve on the accuracy( not that is was not already pretty accurate). The other good news is that there is already a slot in the spindle body for a drift I suppose so drilling and tapping a hole to fix the spindle inside the millhead is a no brainer. It also seems that I can easily remove the gear drive or at least the front shaft and install a custom machined two row pulley setup for a belt drive. I intend to do a similar setup to the tormach machine and try to get around 5k or so spindle RPM. I just bought a Digital handheld tachometer from buy.com and am looking forward to using it to test my theories. The other good news is that it seems like it would be a simple thing to make some aluminum round standoffs to secure a motor mount plate atop the millhead using the six millhead cap screws locations and fab up a motor mount with belt tensioner for a three phase motor and vfd. This should work pretty well and I am excited to give it a try. This plate would also be useful to mount the Pneumatic cylinder for the quick change drawbar. The only real problem is machining a pulley to tightly fit the splined shaft of the spindle. It would be nice if it was available somewhere but I would not even know what it is called.... Any ideas guys.... peace

[whitis]

I see no reason you can't do a QC using belleville washers no matter what kind of machine you have. I suppose the issue being referred to is you have to press down on the drawbar to compress the bellevilles, to release the tool. If you have a quill, that force will tend to try to push the quill down. ...

Seems you are trying to solve problems created by a flawed solution to a previous problem. You want to apply the drawbar force from spindle to drawbar, not from housing (or quill) to drawbar. This doesn't put any force on the spindle bearings (or push on the quill) but does put force on the less critical drawbar bearings. It does, possibly, involve an extra set of thrust bearings because the spindle shaft rotates (but see below). Also, the methods you suggest still put clamping force on the precision spindle bearings - which could be a real problem if it wasn't for the fact that DIY power drawbars don't appear to provide adequate clamping force.

One issue i see with most of the low end power drawbars/ATCs is the clamping force. It appears that professional machines use something like 1 to 4 tons of force. The old fashioned manual drawbar, i.e. a big bolt, can have huge clamping forces. At 100PSI, that is a lot of square inches. I was looking at an air operated vise in a tool catalog, the other day - it looked like its piston was something like 6" diameter. Sure for the smaller machines, you are looking at smaller tools and lower cutting forces and lower speeds (thus less imbalance) so you may not need two tons of clamping force but you still may need a surprising amount - even with manual drawbars, slipping can be an issue on smaller machines. And even the big machines can have trouble with clamping. Grease gets on the toolholders and the spindle taper. So, you may be looking at a serious size pneumatic piston, hydraullics, or a screw mechanism.

Belleville washers gain you nothing in terms of clamping force. Whatever force they exert, you have to exert to release them. And they may come at a potential mechanical price in that you now have to change the direction of applied force in a way that may be less convenient and your length of travel may be limited. One of the things the washers do for you is insure that the system fails in the tool retained mode - so that you don't drop the tool due to a loss of pressure. Though failure to drop the tool before picking up the next might be worse. Another thing the washers do for you is that they make the load on the drawbar bearings occur when the spindle is not rotating. They also may eliminate the need to apply force in more than one direction, though they make it hard to separately control the retention and tool eject forces.

Another possibility with the belleville washers, is to eliminate the drawbar bearings entirely by having the clamping mechanism withdraw far enough that it does not engage either the spindle or the drawbar while the system is not spinning. Overall, it isn't too hard to do it right. You either pinch from the top of the drawbar to an anular disk at the top of the spindle or if that interferes with spindle assembly, you pinch to a disk at the bottom of the spindle, near the nose.

Of course, working with a spindle that wasn't designed to be used for ATC, complicates matters. Enough that it may be easier to replace the spindle. The quill fed machines are more awkward, mechanically.

How much clamping force does one need? Not that easy to answer and depends a lot on the machine, application, etc.
- Needs to exceed any downward forces on the tool encountered during milling.
- Needs to exceed the rotary cutting forces on the tool, scaled by various
mechanical factors, as these are
- If your spindle/toolholders aren't keyed, the force needs to be high enough to prevent slippage in the taper due to the torque required for cutting.
- Needs to exceed the forces of imbalanced tools, tool holders, scaled appropriately. Boring heads, for example, can be hideously imbalanced. Flycutters can also be very unbalanced. Centrifugal forces are proportional to the square of the speed. Some of these forces have a significant mechanical advantage over the drawbar.

The deep tapers used on tool changers are not very good at holding compared to shallow tapers used for collet systems.

On a little sherline spindle with a 3/8-16 draw bar, if you apply 5 pounds of force to a 6" wrench, you are probably providing around 500lbs of clamping force - on a small tool in a shallow taper (i just measured 10pounds on a shorter wrench before the battery in my fish scale died). The shallow taper multiplies that force many times over. Joe Vicar's ATC uses a 1" air cylinder, which would provide about 78lbs at 100psi, and this on a deep taper. Don't think I will try that on a boring bar, fly cutter, milling in a deep pocket, or machining 316. The Hoss ATC for tormach uses a slightly larger cylinder that is capable of providing 176lbs at 100psi.

Tormach doesn't mention the normal tightening force but says "Only a few thousandths of an inch of stretch is needed to generate hundreds of pounds of force by a steel drawbar". They also say their tool holders slip resulting in a Z error of 10mils on heavy cuts - apparently even when dry.

[SCzEngrgGroup]

Seems you are trying to solve problems created by a flawed solution to a previous problem. You want to apply the drawbar force from spindle to drawbar, not from housing (or quill) to drawbar. This doesn't put any force on the spindle bearings (or push on the quill) but does put force on the less critical drawbar bearings. It does, possibly, involve an extra set of thrust bearings because the spindle shaft rotates (but see below). Also, the methods you suggest still put clamping force on the precision spindle bearings - which could be a real problem if it wasn't for the fact that DIY power drawbars don't appear to provide adequate clamping force.

One issue i see with most of the low end power drawbars/ATCs is the clamping force. It appears that professional machines use something like 1 to 4 tons of force. The old fashioned manual drawbar, i.e. a big bolt, can have huge clamping forces. At 100PSI, that is a lot of square inches. I was looking at an air operated vise in a tool catalog, the other day - it looked like its piston was something like 6" diameter. Sure for the smaller machines, you are looking at smaller tools and lower cutting forces and lower speeds (thus less imbalance) so you may not need two tons of clamping force but you still may need a surprising amount - even with manual drawbars, slipping can be an issue on smaller machines. And even the big machines can have trouble with clamping. Grease gets on the toolholders and the spindle taper. So, you may be looking at a serious size pneumatic piston, hydraullics, or a screw mechanism.

Belleville washers gain you nothing in terms of clamping force. Whatever force they exert, you have to exert to release them. And they may come at a potential mechanical price in that you now have to change the direction of applied force in a way that may be less convenient and your length of travel may be limited. One of the things the washers do for you is insure that the system fails in the tool retained mode - so that you don't drop the tool due to a loss of pressure. Though failure to drop the tool before picking up the next might be worse. Another thing the washers do for you is that they make the load on the drawbar bearings occur when the spindle is not rotating. They also may eliminate the need to apply force in more than one direction, though they make it hard to separately control the retention and tool eject forces.

Another possibility with the belleville washers, is to eliminate the drawbar bearings entirely by having the clamping mechanism withdraw far enough that it does not engage either the spindle or the drawbar while the system is not spinning. Overall, it isn't too hard to do it right. You either pinch from the top of the drawbar to an anular disk at the top of the spindle or if that interferes with spindle assembly, you pinch to a disk at the bottom of the spindle, near the nose.

Of course, working with a spindle that wasn't designed to be used for ATC, complicates matters. Enough that it may be easier to replace the spindle. The quill fed machines are more awkward, mechanically.

How much clamping force does one need? Not that easy to answer and depends a lot on the machine, application, etc.
- Needs to exceed any downward forces on the tool encountered during milling.
- Needs to exceed the rotary cutting forces on the tool, scaled by various
mechanical factors, as these are
- If your spindle/toolholders aren't keyed, the force needs to be high enough to prevent slippage in the taper due to the torque required for cutting.
- Needs to exceed the forces of imbalanced tools, tool holders, scaled appropriately. Boring heads, for example, can be hideously imbalanced. Flycutters can also be very unbalanced. Centrifugal forces are proportional to the square of the speed. Some of these forces have a significant mechanical advantage over the drawbar.

The deep tapers used on tool changers are not very good at holding compared to shallow tapers used for collet systems.

On a little sherline spindle with a 3/8-16 draw bar, if you apply 5 pounds of force to a 6" wrench, you are probably providing around 500lbs of clamping force - on a small tool in a shallow taper (i just measured 10pounds on a shorter wrench before the battery in my fish scale died). The shallow taper multiplies that force many times over. Joe Vicar's ATC uses a 1" air cylinder, which would provide about 78lbs at 100psi, and this on a deep taper. Don't think I will try that on a boring bar, fly cutter, milling in a deep pocket, or machining 316. The Hoss ATC for tormach uses a slightly larger cylinder that is capable of providing 176lbs at 100psi.

Tormach doesn't mention the normal tightening force but says "Only a few thousandths of an inch of stretch is needed to generate hundreds of pounds of force by a steel drawbar". They also say their tool holders slip resulting in a Z error of 10mils on heavy cuts - apparently even when dry.

"Drawbar bearings"??? The drawbar is screwed into the tool at the bottom, and the head of the drawbar rides directly on the top of the spindle. There are no "drawbar bearings".

An R8 toolholder requires about 4000-5000 pounds drawbar tension to securely hold a tool in a collet. Less than that, and a 1/2" endmill, or Tormach holder, can pull out on heavy cuts. For a benchtop machine, you can't even make such heavy cuts, so you can get by with a lot less. A rigid holder, like an endmill holder, which does not depend on drawbar tension to retain the tool can get by with a lot less, perhaps 2000 pounds. Large VMCs, with LARGE spindle motors (10HP and up) and CAT50 tooling, typically run on the order of 3000-5000 pounds drawbar tension, provided by a stack of 150 or so large Belleville washers.

Regards,
Ray L.

[ihavenofish]

for reference, a solid iso(bt) 30 taper tool holder is designed to take a maximum 6000 newtons of clamping force. the system is functional at low power with as little as 3000N. these are specifications from various companies that make power drawbars. an iso 25 taper uses a maximum of 4000N, and an iso 20 uses 3000N.

the R8 taper is a shortened version of the iso 30 (or vice versa if you like). because of the lower surface area, the r8 would in theory have more drawbar pull, however given the low torque of most of these spindle, i think 3000-4000N would be quite adequate.

note, these numbers are for SOLID tool holders. a system like the tormach which relies on collet pressure likely needs alot more than the low 3000N number when dealing with alot of torque at the tool.

in any case, an iso/bt 30 splindle shaft will fit anywhere and r8 will, and in the grand sceme of tool costs, and the tool changer itself is probably something worth getting if your machine is on the large side.

to produce the required tension, you need about 120-150 disc spring, 20mm diametre, creating a stack about 6" long and having 6mm of travel. if the spindle is designed correctly, the springs can easily fit inside the shaft. release force if you started with 5000N (to be safe) is in the range of 8000-10000N, which is up to 2250lbs.

on smaller machines, iso25 might be a better choice, however theres not really an abundance of tooling available.

[philbur]

I think you guys are missing one big difference between ISO/BT and R8. ISO/BT has drive dogs so slippage under load due to a low draw bar pull is not an issue., where as an R8 has no drive dogs so slippage under load is only prevented by co-efficient of friction, consequently it will require more pull on the drawbar.

Phil

PS: The key on the R8 is not intended for drive only to prevent the R8 from spinning when screwing the drawbar in or out.

[ihavenofish]

I think you guys are missing one big difference between ISO/BT and R8. ISO/BT has drive dogs so slippage under load due to a low draw bar pull is not an issue., where as an R8 has no drive dogs so slippage under load is only prevented by co-efficient of friction, consequently it will require more pull on the drawbar.

Phil

PS: The key on the R8 is not intended for drive only to prevent the R8 from spinning when screwing the drawbar in or out.

actually, iso30 does NOT have drive notches on the flange, though BT and CT 30 do. it seems many smaller 30 taper spindles do not even have provision for dogs as they arent needed below a certain amount of torque.